1) Field of the Invention
The present invention relates to a non-contact IC tag system including a plurality of non-contact IC tags that has identification information for identifying the non-contact IC tags, and includes a storage unit for storing a predetermined data amount, respectively, and a reader/writer that sends operation commands via radio to each of the non-contact IC tags, and more particularly, to a non-contact IC tag system that can handle large data efficiently with a non-contact IC tag that is mass-produced with a low cost and a small memory capacity.
2) Description of the Related Art
Conventionally, a technology in which barcodes are given to various products in a shop and a cashier reads the barcodes using a barcode reader is known. Recently, a non-contact Radio Frequency Identification (RFID) tag (hereinafter, “IC tag”) is often used instead of the barcode. With the IC tag, information can be updated and added, and plural individuals can be recognized collectively. Thus, the IC tag attracts attentions as an individual recognition technology in the next generation substituting for the barcode.
Such an IC tag includes a silicon chip that contains a memory and an antenna that can transmit data by radio. Since various data can be stored on this memory, the IC tag is used in various fields as a kind of an information storage.
For example, Japanese Patent Application Laid-Open No. 2001-307055 discloses an IC tag that is constituted to store secret information for each stage in a life cycle from production to disposal. In addition, Japanese Patent Application Laid-Open No. 2004-133596 discloses a monitoring system that is constituted to store measurement information obtained by various sensors disposed in a plant and transmit this measurement information to a plant failure diagnosis apparatus.
In the conventional IC tag, necessary data is stored in a memory in an IC chip by a necessary amount while changing a memory capacity in the IC tag as occasion arises according to an application (disposed place) of the IC tag. In other words, since each IC tag can function within a range of the memory capacity implemented in the IC tag, it is necessary to implement a necessary and sufficient memory capacity in each IC tag.
However, such an IC tag is not essentially of a nature to change a memory capacity appropriately according an application thereof and does not have significance unless IC tags of an identical standard is produced in a large quantity to reduce overall cost. This is because, if cost for introducing the IC tag is too large, it is less expensive to use a barcode. In other words, although it is technically possible to mount a memory with a large capacity on an IC tag used for a special application, since production cost for such an IC tag increases naturally, it is inefficient to change a memory capacity of the IC tag according a system.
On the other hand, since it is expected that such an IC tag will be used more widely in various fields in future, needs for an IC tag handling a lager amount of data are considered to increase. For example, when it is desired to maintain data of temperature and humidity history management, positional information, and the like of wine, meat, and the like on an IC tag for a long period of one week, the IC tag is required to be capable of handling a large amount of data.
Consequently, an extremely important problem is how to handle large data efficiently while using an IC tag that is produced in a large quantity and inexpensive and has a small memory capacity. In particular, such a problem is conspicuous when an IC tag is used in a monitoring system.